body {
  margin: 0;
  height: 100vh;
  display: flex;
  justify-content: center;
  align-items: center;
  background-color: black;
  overflow: hidden;
}

.container {
  position: relative;
  width: 40em;
  height: 40em;
  font-size: 20px;
}

.sun {
  position: absolute;
  top: 15em;
  left: 15em;
  width: 10em;
  height: 10em;
  border-radius: 50%;
  box-shadow: 0 0 3em white;
  /* 为了看到太阳自转的效果，我添加了头像进去 */
  background: yellow url("./tx.jpg") center/contain no-repeat;
  animation: orbit 36.5s linear infinite;
}

.earth,
.moon {
  position: absolute;
  border-style: solid;
  border-color: white transparent transparent transparent;
  border-width: 0.1em 0.1em 0 0;
  border-radius: 50%;
}

.earth {
  top: 5em;
  left: 5em;
  width: 30em;
  height: 30em;
  animation: orbit 36.5s linear infinite;
}

.moon {
  top: 0;
  right: 0;
  width: 8em;
  height: 8em;
  animation: orbit 2.7s linear infinite;
}

.earth::before,
.moon::before {
  content: "";
  position: absolute;
  border-radius: 50%;
}

.earth::before {
  top: 2.8em;
  right: 2.8em;
  width: 3em;
  height: 3em;
  background-color: aqua;
}

.moon::before {
  top: 0.8em;
  right: 0.2em;
  width: 1.2em;
  height: 1.2em;
  background-color: silver;
}

@keyframes orbit {
  to {
    transform: rotate(360deg);
  }
}
